Problem: The following line passes through point $(3, 1)$ : $y = -1 x + b$ What is the value of the $y$ -intercept $b$ ?
Explanation: Substituting $(3, 1)$ into the equation gives: $1 = -1 \cdot 3 + b$ $1 = -3 + b$ $b = 1 + 3$ $b = 4$ Plugging in $4$ for $b$, we get $y = -1 x + 4$. ${1}$ ${2}$ ${3}$ ${4}$ ${5}$ ${6}$ ${7}$ ${8}$ ${9}$ ${10}$ ${\llap{-}2}$ ${\llap{-}3}$ ${\llap{-}4}$ ${\llap{-}5}$ ${\llap{-}6}$ ${\llap{-}7}$ ${\llap{-}8}$ ${\llap{-}9}$ ${\llap{-}10}$ ${1}$ ${2}$ ${3}$ ${4}$ ${5}$ ${6}$ ${7}$ ${8}$ ${9}$ ${10}$ ${\llap{-}2}$ ${\llap{-}3}$ ${\llap{-}4}$ ${\llap{-}5}$ ${\llap{-}6}$ ${\llap{-}7}$ ${\llap{-}8}$ ${\llap{-}9}$ ${\llap{-}10}$ $(3, 1)$